<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>css3</title>
    <style>

          .box{
              width: 100px;
              height: 100px;
              background-color: green;
              border-radius: 20px; /*相对单位-绝对单位*/
              box-shadow: 8px 7px 8px 3px grey,8px 7px 8px 3px grey;
              text-shadow: 1px 2px 4px gray;
              line-height: 100px;
              font-weight: 900;
              font-size: 15px;
              color: white;
          }

    </style>
</head>
<body>
<div class="box">

    hello world
</div>
</body>
</html>